How much is HBO and is it worth it?

I’m thinking about purchasing HBO because I’ve recently become a fan of “True Blood” and I don’t want to wait for the third season to come out on DVD but I’ve been looking online for pricing and I can’t find anything! I want to know about how much more I would be looking at per month and for those of you who have HBO or have had it in the past, is it worth paying the extra money?